Rotor safety lock for munition fuze



Nov. 17, 1964 LOHMANN 3,157,125

ROTOR SAFETY LOCK FOR MUNITION FUZE Filed July 1, 1963 IN VENTOR. JPrA me A! day/MAW WWW pea 40M United States Patent fifi'ce EJSZEZE Patented Nov. 1?, lfifid 3,157,125 RDTQR SAFETY LUCK FUR MUNTTHGN FUZE Arthur M. Lohmann, Hopkins, Minn, assignor to Honeywell Inc, a corporation of Delaware Filed duly 1, 1963, Ser. No. 291,894 '7 Claims. (Cl. Till-7%) This invention relates generally to a delayed arming device for a munition fuze and more particularly to a safety lock for a munition fuze having a rotor or other carrier member movable between a safe position and an armed position.

In modern fusing systems for munitions it is common practice to require that a predetermined sequence of events take place before detonation of the fuze is allowed to occur. The pu pose of such a sequence is to insure that the munition can be handled safely prior to being used and that the fuse will detonate at the proper time after the launch of the munition in which it is used.

In the present fuze, a detonator or other initiating means is carried by a rotor or carrier member between a safe position out of line with a firing pin and an armed position in line with the firing pin. Prior to launch the rotor is retained in the safe position by two independently operated mechanisms. The first is a setback pin which mechanically engages the rotor until subjected to the high setback force incident to launch of the munition. The force required to operate the setback pin is sufficiently high that the shocks experienced during normal handling will not effect its operation. The second mechanism holding the rotor in the safe position is the firing pin which engages a cup in the rotor surface. The firing pin is spring biased away from the cup out is held in the cup until the munition is launched. Although the details of the mechanism holding the firing pin in the cup are not disclosed on the attached drawings, it should be apparent that a variety of devices are suitable. For example, a mechanical safety pin or lanyard could hold the firing pin in place until its removal at launch. If the munition is rotated after launch, centrifugally operated detents could also be used.

After launch, the setback pin and the firing pin no longer engage the rotor. Means are then provided to drive the rotor from the safe position to the armed position at a predetermined rate of speed. In the preferred embodiment a coiled spring is used to provide power to drive the rotor, and an escapement mechanism delays the rotation.

When the rotor reaches the armed position, the detonator is in line with the firing pin. The firing pin can then be driven into the detonator to initiate an explosion. The means used to drive the firing pin can be impact operated, operated by a timer, or can be made responsive to atmospheric pressure variations or radio signals. This feature is not important to the invention and is thus not disclosed in detail. The sequence of events necessary for the basic operation of the fuze is therefore as follows: a first event (launch) releases the rotor. The rotor moves to the armed position within a preset time period. A second event (impact) then detonates the fuze.

The present invention relates to an additional safety feature to be incorporated in the above described fuze to prevent arming of the fuze in certain Well defined although unusual circumstances. Assume that the fuze is to be used in a munition which is ejected from a dispenser tube carried by an aircraft. The force of ejection from the tube operates the setback pin to release the rotor and a bore-riding safety pin (not shown) is used to release the firing pin from the cup in the rotor. The bore-riding safety pin is a spring loaded pin which rides the inner surface of the bore until the munition leaves the dispenser tube. The pin is then ejected to release the firing pin from the cup in the rotor. The principle of a bore-riding safety pin is explained in the Woodberry Patent 2,118,062, which issued May 24, 1938. At this point the rotor is free to move to the armed position. After reaching the armed position, the fuze is ready to be detonated upon the occurrence of the second event, in this case an impact with the ground.

An extremely dangerous situation occurs if the munition is accidently ejected from the tube after the aircraft has been armed. This situation can occur if the aircraft has been airborne and its despenser tubes have been fired. If one of the tubes fails to fire, the munition will remain in the tube and could easily be ejected when the aircraft lands. An aircraft landing on a carrier deck for example, experiences high-G forces when brought to a sudden stop. These intertial forces would tend to expel a munition from the dispenser tube. It the fuze has at some time been subjected to sufiicient setback force to free the setback pin from the rotor, the rotor would be free, after ejection of the munition from the tube, to move to the armed position. After ejection, the munition would tend to skip or bounce along the landing area or carrier deck and would explode on the first impact occurring after the rotor reached the armed position. Although the chance of this series of events occurring is statistically small, the disastrous results of an explosion in a crowded landing area require that steps be taken to reduce the probability of accidental explosion even further. In some applications of this fuze, the setback pin is not used. The rotor is then held in the safe position by the firing pin alone. Such a fuze is more dangerous since one less step in the sequence is required to arm the fme.

The inventive concept hereafter described embodies a rotor safety lock to prevent an explosion if the above described series of events occurs. A tightly coiled helical spring is placed in an annular groove in the face of the rotor extending from the detonator to the open cup. The coiled spring is thus in line with the firing pin at all times during movement of the rotor from the safe position to the armed position. The firing pin itself :is conical in shape and is connected at its base to a firing pin spring with a shaft having a diameter smaller than the base. A barbed or hooked firing pin results which will penetrate the coiled spring and engage therein to lock the rotor in a non-armed position if impact occurs while the rotor is moving from the safe position to the armed position. With the firing pin firmly locked in the coiled spring in the rotor, there is no possibility of initiating the detonator upon subsequent impacts.

It is therefore a primary purpose of the invention to provide in a munition fuze an additional safety feature in the form of a rotor safety lock.

Another object of the present invention is to provide a safety feature which can easily be incorporated in any munition fuze utilizing a firing pin and a movable rotor or carrier member.

'A further object is to provide a safety device which will dud a munition fuze if impact occurs prior to its attaining the armed condition.

Yet another object of the present invention is to provide an additional safety feature for a munition fuze which will in no way reduce the reliability or effectiveness under normal operating conditions.

Gther objects of this invention will be apparent from the specification and claims when considered in connection with the accompanying drawings, in which:

FIGURE 1 is a top plan view of the fuze with the rotor in the safe position;

FIGURE 2 is a longitudinal sectional view of the fuze with the rotor in the safe position;

FIGURE 3 is a top view of the tuze in the armed position;

53 FIGURE 4 is a longitudinal sectional view of the fuze in the armed position;

FIGURE 5 is a top view of the fuze showing the rotor locked between the safe position and the armed position;

and

FIGURE 6 is a fragmentary longitudinal sectional view taken along line 6-6 of FIGURE 5.

' ber 14 consisting of'a'series of donnected sections as dis-" closed in FIGURE 2. Body member 14 is composed of a series of sections in order that the fuze may be more easily assembled and the cost reduced. Contained within body member 14 is a hollow chamber 16 in which the various fuze elements are mounted.

The heart of the fuze assembly is the rotor or carrier member 18 which is rotatably mounted on an axis 20; axis 20 being mounted in parallel with the longitudinal axis of the projectile. Rotor 18 is a cylindrical section having an upper surface 19 and a lower surface 21. Attached to lower surface 21 of rotor 18 is a generally circular disk member 22 which extends beyond the periphery of rotor 18. The edge of disk member 22 is 1 provided with teeth 24 which extend approximately oneshown in FIGURE 1, teeth 24 do not mesh with pinion 26 in the safe position. v

To provide motive power to drive rotor 18 from a safe position to an armed position, a coiled spring 30 is provided. Coiled spring 30 is firmly attached to body member 14 at end 32, and the other end 34 is attached to a pin 36 on disk member 22. Spring 30 is shown in FIGURE 1 in the fully extended position.

To hold the rotor in the safe position shown in FIG- URE 1,.a setback pin 38 is mounted within body member 14 so as to engage a hole 39 in disk member 22. Setback pin 38 is supported by a pair of flexible metal straps 40 and 42 which are adapted tobend when setback pin 38 is exposed to an inertial force upon launch. Setback pin 38 is thus forced to the rear upon launch as disclosed in FIGURE 4 to disengage disk member 22.

A flat spring arm 44 is mounted within chamber 16. One end 46 of spring arm 44 is attached to body member 14 andthe free end lies adjacent upper surfaces 19 of rotor 18. A cone-shaped firing pin 48 is attached to the free end of spring arm 44 by a shaft 50 having a diameter smaller than the base of the firing pin 48. An open cup 52 isformed in upper surface 19 of rotor 18 so as to be in line with firing pin 48 in the safe position. Also mounted in the rotor is a detonator 54 which is out of line with firing pin 48 in the safe posiiton. An open annular groove 56 has also been formed in the upper surface 19 of rotor 18 between cup 52 and detonator 54. Contained within groove 56 is a tightly coiled spring 58.

Also disclosed in FIGURE 2 is a primer charge 60 mounted in body member 14 which extends from a point adjacent the rotor 18 to a point on the surface of container 12. With rotor 18 in the safe position, primer 60 is out of line with detonator 54.

The mechanism which operates the firing pin has not been disclosed in these drawings except for an intermediate pin 62 which extends through an opening in the upper surface of body member-14. In FIGURE 2, the firing pin operating means (not shown) is holding pin 62 against spring arm 44 so that firing pin 48 is forced into cup 52 in rotor 18. This feature aids setback pin 38 in holding rotor 18 in the safe position and in some appli- 4 cations may be the only device holding the rotor in the safe position.

Referring now to FIGURES 3 and 4, the fuze is shown in the armed position. Due to the inertial force resulting from the launch, setback pin 38 has been disengaged from disk member 22 and is being held out of engagement by metal straps 40 and 42. In addition, a bore-riding safety pin (not shown) has been removed upon launch to allow pin 62 to move upwardly in the opening in body member 14. This movement of pin 62 allows spring arm 44 to assume its normal position in parallel with upper surface 19 of rotor 13. This movement of spring arm 44 removes firing pin 48 fro open cup 52 to release rotor 18.

After firing pin 48 and setback pin 38 disengage rotor 18, spring 30 is free to drive rotor'18' in a counterclockwise direction at a speed determined by escapement mechanism 28. Teeth 24 of disk member 22 engage pinion 26 during rotation to provide the necessary con: nection between rotor 18 and escapement mechanism 28. The period of time required for rotor member 18 to go from the safe position to the armed position is determined by the gear ratios and spring selected and by the characteristics of the escapement mechanism.

In the armed position shown in FIGURE 4, the firing pin 48 is in line with detonator 54which in turn is in line with primer 619. If an impact occurs, the impact detecting mechanism (not shown) will force down pin 62 against spring arm 44 to drive firing pin 48 into detonator 54. The resulting explosion of detonator 54 will in turn ignite primer 69; the explosion of which can be used to detonate the munition warhead. It is noted that once the rotor reaches the position shown in FIGURE 4,

the warhead will detonate upon the first impact occuring.

FIGURE 5 discloses a top view of the fuze in which the rotor has left the safe position but has not yet reached the armed position. During the period of rotation,

groove 56 and coiled spring 58 are always in line with firing pin 48. If an impact occurs prior to the time that the rotor reaches the armed position, firing pin 48 will be driven into coiled spring 58 and will lock therein due to the barbed construction of the firing pin. With firing pin 48 locked in spring 58, rotor 18 is no longer free to continue rotation to the armed position and will remain locked in a non-armed position. This locking fea ture is clearly disclosed in FIGURE 6. FIGURE 6 is a view taken along line 6-6 in FIGURE 5. In the locked position, firing pin 48 has penetrated spring 58 and cannot be released. Operation Prior to launch the fuze is in the safe position shown in FIGURES l and 2. Rotor 18 is held in the safe position by setback pin 38 and by firing pin 48. Upon launch, a bore-riding safety pin (not shown) releases pin 62 which allows spring arm 44 to assume its normal position as shown in FIGURE 4. The inertial force upon launch frees setback pin 38 from engagement with rotor 18 thus allowing coil spring 30 to begin the counterclockwise rotation of rotor 18 from the safe position to the armed position. If the flight is normal, rotor 18 will reach the armed position shown in FIGURES 3 and 4 after a predetermined period of time. A subsequent impact will be sensed by appropriate means (not shown) which will act upon pin 62 to drive firing pin 48 into detonator 54.

The invention claimed herein relates to the safety. device which includes barbed firing pin 48 and coil spring 58 lying in groove 56 of rotor 18. If the munition is accidentally ejected from the dispenser tube as described in the introduction of this specification or is otherwise accidentally dropped in a condition to begin arming, the first impact occurring will drive firing pin 48 into spring 58 to lock the rotor in a non-armed position. Any number of subsequent impacts which may occur will have no effect upon the fuze since it is effectively locked in a nonarrned position. r

It is apparent that this invention can be incorporated into any munition fuze which utilizes a carrier member which moves from a safe position to an armed position at a predetermined rate of speed. It is not necessary that the carrier member be a circular rotor as it may well be a simple slider having linear rather than rotational movement. It should also be clear that the particular configuration of firing pin disclosed in the drawings is not critical. Any shape will suflice for a firing pin as long as it can perform the dual function of initiating the detonator and locking in a coiled spring or other engaging device. In an electrically operated fuze, for example, the firing pin could be replaced by some form of contacting pin and the detonator replaced by a suitable mated initiating means.

From the above description it will be apparent that l have invented a new and unique safety feature for a munition fuze having a movable carrier member. Although the form of the invention described herein constitutes a preferred embodiment, it will be understood that changes may be made Within the spirit of the invention limited only by the scope of the appended claims.

I claim as my invention:

1. A fuze for a barrel launched munition subjected to setback force upon launch, comprising: a hollow cylindrical body member with first and second closed ends each having a tubular passageway formed longitudinally therein; a primer cup mounted in said passageway in said first end; a rotor mounted within said body member and being rotatable between a safe position and an armed position about a concentric axis of rotation located at a predetermined distance from said primer cup and parallel thereto with a radius of said rotor being greater than said predetermined distance; setback operated detent means mounted in said first end of said body member engaging said rotor to thereby retain said rotor in said safe position until a setback force is received upon launch; driving means mounted in said body member to rotate said rotor from said safe position to said armed position; clock escapement means mounted in said body member and engageable with said rotor to thereby regulate the speed of rotation of said rotor; said rotor having a tubular passageway formed therein at said predetermined distance from sm'd axis aligned with said primer cup in said armed position; a detonator mounted in said rotor passageway; said rotor having a cup formed therein facing said second end at said predetermined distance from said axis in line with said primer cup in said safe position; a fiat firing pin spring member attached at one end to said body member and lying between said rotor and said second end, and said firing pin spring member being biased away from said rotor; a cone shaped firing pin connected to said firing pin spring member by a shaft having a diameter smaller than the base of said conical firing pin so as to be in line with said cup in said safe position and with said detonator in said armed position; impact sensing means mounted in said passageway in said second end adapted to hold said firing pin in said cup in said safe position and to release said firing pin after launch to allow said rotor to rotate to sm'd armed position; said rotor having an open annular groove facing said second end formed therein between said cup and said detonator; a tightly coiled helical spring mounted longitudinally in said groove; said impact sensing means driving said firing pin into said detonator upon an impact occurring after said rotor reaches said armed position but said conical firing pin being adapted to snap into and engage said helical spring if impact occurs during rotation of said rotor to thereby lock said rotor in a non-armed position.

2. An inertial fuze for a gun launched munition, comprising; a body member having a chamber therein; a rotor having first and second sides and a peripheral edge connecting said sides mounted in said chamber and rotatable about a central axis between a safe position and an armed position; a fiat spring member having a first end attached to said body member in said chamber and a second end disposed adjacent said first side of said rotor between said axis and said peripheral edge, and said spring member being biased away from said rotor; at cone-shaped firing pin having a circular base connected to said second end or" said spring member by a shaft having a diameter smaller than the diameter of said base; a detonator mounted in said rotor in line with said firing pin in said armed position; said first side of said rotor having a cup formed therein in line with said firing pin in said safe position; impact sensing means mounted in said body iember adapted to hold said firing pin in said cup in said safe position and to release said firing pin upon launch; driving means mounted in said chamber to rotate said rotor from said safe position to said armed position upon release of said firing pin from said cup; delay means mounted in said chamber and engageable with said rotor to thereby regulate the speed of rotation of said rotor; said rotor having an annular groove formed in said first side between said detonator and said cup; and a coiled spring mounted longitudinally in said groove; said impact sensing means driving said firing pin into said detonator upon impact occurring in said armed position but said impact sensing means driving said firing pin into said coil spring to thereby lock said rotor in a non-armed position if said impact occurs prior to said rotor reaching said armed position.

3. An inertial tune for a munition subjected to a setback force upon launch, comprising; a body member having a chamber therein; a rotor mounted in said chamber and rotatable about an axis between a safe position and an armed position; a spring member attached to said body member in said chamber and disposed adjacent said rotor, and said spring member being biased away from said rotor; a cone-shaped firing pin having a circular base connected to said spring member by a shaft having a diameter smaller than the diameter of said base; a detonator mounted in said rotor in line with said firing pin in said armed position and said rotor having a cup formed therein in line with said firing pin in said sate position; impact sen-sing means mounted in said body member adapted to hold said firing pin in said cup in said safe position and to release said firing pin after setback; driving means mounted in said chamber to rotate said rotor from said safe position to said armed position upon release of said firing pin from said cup; delay means mounted in said charnber and engageable with said rotor to thereby regulate the speed of rotation of said rotor; said rotor having an annular groove formed therein between said detonator and said cup; and a coiled spring mounted in said groove; said impact sensing means driving said firing pin into said detonator upon an impact occurring in said armed position but said impact sensing means driving said firing pin into said coiled spring to thereby lock said rotor in a non-armed position if said impact occurs prior to said rotor reaching said armed position.

4. A munition fuze subject to setback and impact f rces, including: a resiiiently mounted firing pin; a movable carrier member having a first area thereon opposite said firing pin in a safe position and a second area thereon opposite said fining pin in an armed position; means for normally holding said carrier member in said safe position and for releasing said carrier member upon the occurrence of said setback force; means for driving said carrier member from said safe position to said armed position at a predetermined speed upon being released; a detonator mounted in said carrier member at said second area; means for driving said firing pin into said detonator upon the receipt of said impact force; and fining pin engaging means mounted in said carrier member between said first area and said second area to engage with and lock said firing pinto thereby iocl; said carrier member should said impact occur prior to said carrier member reaching said armed position.

5. A inunition fnze subiect to setback and impact forces, including: a resiliently mounted barbed firing pin; a movable carrier member having .a first area thereon in line with said firing pin in :a safe position and a second area thereon in line with said firing pin in an armed position; means for normally holding said carrier member in said safe position and for releasing said carrier member upon the occurrence of a setback force; means for driving said carrier member from said safe position to said armed .position at a predetermined speed upon being released; a. detonator mounted in said carrier member at said second area; means for driving said firing pin into said detonator upon the receipt of an impact force; andcoiled spring means mounted in an open groove in said carrier member between said first area and said second area to engage said barbed firing pin to lock said carrier member should said imp-act occur prior to said carrier member reaching said armed position.

6. A munition fuze subject to first and second events, including: a resiliently mounted firing pin; a movable carrier member having a first area thereon in line with said firing pin in a safe position and a second area thereon in line with said firing pin in an armed position; means for norm-ally holding said carrier member in said safe position and for releasing said carrier member upon the occurrenc'e of said first event; means for driving said carrier member from said safe position to said armed position upon being released; means connected with said carrier member for delaying the movement thereof; a detonator mounted in said carrier member at said second area; means for driving said firing pin into said detonator upon the occurrence of said second event with said carrier member in said armed position; and firing pin engaging means mounted in an opening in said carrier member between said first area and said second area to engage said firing :pin to lock said carrier member should said second event occur subsequent to said carrier member leaving said safe position and prior to said carrier member reaching said armed position.

7. A munition fuze subject to first and second events,

comprising: contacting pin means having hook means formed thereon; a movable carrier member having a first are-a thereon in line vwith said pin means in a safe position, a second area thereon in line with said pin means in an armed position, and an intermediate area thereon between said first and second areas; means for norm-ally holding said carrier member in said safe position and for releasing said carrier member upon the occurrence of said first event; means including delay means for driving said carrier member from said safe position to said armed position at a predetermined speed upon being released; said intermedi:

ate area being in line with said hook means during movement of said carrier member from said safe to said armed position; detonation initita-ting means mounted in said carrier member at said second area; means for driving said pin means into said initiating means with said carrier member in'said armed position upon the occurrence of said second event; and hook engaging means mounted in said intermediate area of said carrier member to engage said hook means to lock said carrier member should said second event occur subsequent to said carrier member leaving said safe position and prior to said carrier member reaching said armed position.

References Cited in the file of this patent UNITED STATES PATENTS 

4. A MUNITION FUZE SUBJECT TO SETBACK AND IMPACT FORCES, INCLUDING: A RESILIENTLY MOUNTED FIRING PIN; A MOVABLE CARRIER MEMBER HAVING A FIRST AREA THEREON OPPOSITE SAID FIRING PIN IN A SAFE POSITION AND A SECOND AREA THEREON OPPOSITE SAID FIRING PIN IN AN ARMED POSITION; MEANS FOR NORMALLY HOLDING SAID CARRIER MEMBER IN SAID SAFE POSITION AND FOR RELEASING SAID CARRIER MEMBER UPON THE OCCURENCE OF SAID SETBACK FORCE; MEANS FOR DRIVING SAID CARRIER MEMBER FROM SAID SAFE POSITION TO SAID ARMED POSITION AT A PREDETERMINED SPEED UPON BEING RELEASED; A DETONATOR MOUNTED IN SAID CARRIER MEMBER AT SAID SECOND AREA; MEANS FOR DRIVING SAID FIRING PIN INTO SAID DETONATOR UPON THE RECEIPT OF SAID IMPACT FORCE; AND FIRING PIN ENGAGING MEANS MOUNTED IN SAID CARRIER MEMBER BETWEEN SAID FIRST AREA AND SAID SECOND AREA TO ENGAGE WITH AND LOCK SAID FIRING PIN TO THEREBY LOCK SAID CARRIER MEMBER SHOULD SAID IMPACT OCCUR PRIOR TO SAID CARRIER MEMBER REACHING SAID ARMED POSITION. 